I think it will all depend upon exactly what he does.
The best thing to do would be to check on his firms intranet if they have one, or make an anonymous call to their HR department to see what the stance is.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley. http://kallis3.blogs.iva.co.uk
An enquiry with his HR department would resolve any doubts and all enquiries of this nature should be treat in a confidential manner. The Anonymous enquiry would perhaps be the best option though!
If he is FSA Regulated then yes an IVA can and has caused problems in the past for people. As Jan suggested above I would make an anonymous call to HR asking for their stance on it for someone already employed and check any internal literature they have on their intranet of their financial expectations/requirements of their employees.